Time-interleaved analog-to-digital converter for signals in any Nyquist zone

Abstract

Processing a signal by receiving an analog input signal located outside of a first Nyquist zone that is between 0 and fs / 2; passing the analog input signal through an M-channel time-interleaved analog-to-digital converter (TI-ADC) to generate a TI-ADC output signal; and estimating and correcting a timing skew error in the TI-ADC output signal. Alternatively, an electronic circuit that includes an input for an analog input signal, an M-channel time-interleaved analog-to-digital converter (TI-ADC) and a timing skew error estimating and correcting circuitry. The analog input signal is located outside of a first Nyquist zone that is between 0 and fs / 2. The TI-ADC receives the analog input signal and generates a TI-ADC output signal. The timing skew error estimating and correcting circuitry estimates and corrects a timing skew error in the TI-ADC output signal.

Description

RELATED PATENT APPLICATION[0001]This application claims priority to U.S. Provisional Patent Application No. 61 / 535,959 filed Sep. 17, 2011, entitled “Time-Interleaved Analog-to-Digital Converter for Signals in any Nyquist Zone,” and which is hereby incorporated by reference for all purposes.BACKGROUND OF THE INVENTION[0002]Time-interleaving of two, or more, analog-to-digital converters (ADCs) is a common way to overcome the limits of hardware technology that affect the maximum sampling frequency fS for a single ADC. Time-interleaved analog-to-digital converters (TI-ADCs) offer a significant increase in the available sample rate of ADCs. In other words, for example, by using two TI-ADCs operating in parallel with a Ts time offset of their 2Ts time interval sampling clocks (i.e. a 180-degree phase shift in the sampling clocks), the overall sampling frequency of the system is doubled. In an ideal two-channel TI-ADC, aliasing terms formed by the individual ADCs, operating at half rate, ...

AI Technical Summary

Benefits of technology

This approach effectively corrects timing skew errors for signals in any Nyquist zone, improving the performance of TI-ADCs by allowing continuous operation and accurate spectral component cancellation, even for band-pass signals above the first Nyquist zone, thereby enhancing the overall sampling process.

Problems solved by technology

The performance of TI-ADCs is degraded by timing and gain mismatches.

The sample instants of the individual time-interleaved ADCs are affected by an unknown and possibly slowly varying with environment time delay, Δtm, which results in an undesired frequency dependent phase offset of their aliased spectra that prevents their perfect cancellation at the output of a time multiplexer.

Mismatches in path gains, gm, of the TI-ADC, due to the tolerance spread of analog components, are always present in the ADC's hardware.

The first approach has the disadvantage that normal TI-ADC operations are suspended during the probe while in the second approach the calibration process does not interrupt normal operation.

In other words, a common problem is the removal of undesired signal artifacts related to timing and gain imbalances between interleaved analog-to-digital converters.

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